Amount of training and cue-evoked taste-reactivity responding in reinforcer devaluation.

Abstract

In two experiments, rats received minimal (16) pairings of one auditory conditioned stimulus (CS) cue with a sucrose reinforcer, and extensive (112) pairings of another auditory CS with that reinforcer. After sucrose was devalued by pairing it with lithium chloride in some rats (Devalue groups) but not others (Maintain groups), taste reactivity (TR) and other responses to unflavored water were assessed in the presence of the auditory CSs alone. The minimally-trained CS controlled substantially more evaluative TR responses than the extensively-trained CS. Those TR responses were hedonic (positive) in the Maintain groups, but aversive (negative) in the Devalue groups. By contrast, food cup entry and other responses thought not to reflect evaluative taste processing were controlled more by the extensively-trained cue. These responses were reduced by sucrose devaluation to a similar extent regardless of the amount of training. The results suggest rapid changes in the content of learning as conditioning proceeds. Early in training, CSs may be capable of activating pre-evaluative processing of an absent food reinforcer that includes information about its palatability, but that capability is lost as training proceeds. Keywordsassociatively-activated event representations; contents of learning; devaluation; taste reactivity Considerable evidence shows that the contents of associative learning change over the course of extended training. Typically, learned performance is thought to be more flexible and goaloriented in early stages of training, but becomes increasingly automatic and less governed by its consequences with more extended training (e.g., Allport, 1937;Kimble & Perlmuter, 1970;Tolman, 1948.) Adams and Dickinson (1981) suggested that extended training may be accompanied by a shift from the control of behavior by outcome expectancies (stimulusreinforcer or response-reinforcer associations) to control by stimulus-response associations. Consistent with this view, several investigators have found that after extended instrumental training, responding is less sensitive to reinforcer devaluation (e.g. Adams, 1982;Bussey et al., 1996; but see Colwill & Rescorla, 1985;Holland, 2004), a primary indicant of the mediation of performance by outcome expectancies (Pickens & Holland, 2004). For example, Adams (1982) found that after small amounts of food-rewarded lever press training, devaluation of the food by pairing it with a toxin resulted in spontaneous reductions in lever pressing in the absence of food, whereas comparable food devaluation after extended lever press training left responding unaffected.Corresponding author: Peter C. Holland, 3400 North Charles Street, 222 Ames, Baltimore, MD 21218 USA, Voice: 1 410 516-6396, FAX: 1 410 516-0494, pch@jhu.edu. HL is now at the University of North Carolina, Chapel Hill and IA is now at Harvard University. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptOther evidence suggests that the content of learning may change more sub...

On the nature of CS and US representations in Pavlovian learning

“…Holland, Lasseter, and Agarwal (2008) recently extended an earlier finding of Holland (1998) in which it was demonstrated that mediated conditioning but not US devaluation effects are affected by the amount of CS-US training trials administered prior to the critical treatment. For instance, Holland, et al (2008) demonstrated that the influence of an auditory cue for sucrose upon the rats’ taste reactivity responses to plain water is diminished as the number of CS-US pairings is increased. However, at the same time, these authors also reported that the number of training trials did not reduce the sensitivity of the auditory-cue-evoked magazine approach response to sucrose devaluation.…”

Cognitive versus stimulus-response theories of learning

“…In addition, in both delivery conditions, simple licking responses, characterized by Berridge (2000) as consummatory but nonhedonic, showed moderate but not complete sensitivity to devaluation. Thus, the results of Holland et al's (2008) study suggest that, regardless of reinforcer delivery method, evaluative TR responses are especially sensitive to devaluation, compared to nonevaluative consummatory responses (simple licking), and (with conventional delivery) to appetitive responses (food cup entry).…”

“…Consistent with that possibility, Colwill and Rescorla (1990) found nearly complete devaluation of operant lever pressing after training and devaluation with intraoral reinforcer delivery. More recently, Holland, Lasseter and Agarwal (2008) examined consummatory and TR responses in devaluation experiments with either intraoral or conventional (to a recessed cup) delivery of sucrose reinforcers. The food cups were equipped with cameras to permit measuring TR responses in the cup condition as well as the intraoral delivery condition.…”

Model-based and model-free Pavlovian reward learning: Revaluation, revision, and revelation

“…However, it is only one exemplar of a wider and long-studied class of revaluation changes in Pavlovian responses that we suggest demand explanation in terms of similar model-based mechanisms, involving stimulus-stimulus associations that preserve the details about the identities of events that have been learned (Dickinson, 1986; Holland, 1990; Holland, Lasseter, & Agarwal, 2008) (Bouton & Moody, 2004; Holland et al, 2008; Rescorla, 1988; Rizley & Rescorla, 1972; Zener & McCurdy, 1939). In all of these, individuals show that they can use learned information about the identity of a UCS that is associated with a particular CS when new information is later added to that CS (for example, developing a taste aversion to an absent UCS, when its associated CS later becomes paired associatively with illness (Holland, 1990).…”

“…Although we discuss some differences later, there are further similarities between Pavlovian and instrumental effects of extensive training. For instance, it has been observed (Holland et al, 2008) that the predictive capacities of first-order appetitive CSs (which are directly associated with UCSs) are immediately affected by UCS revaluation, whereas second-order CSs (whose associations are established via first order CSs) are less influenced (Holland & Rescorla, 1975; Rescorla, 1973; Rescorla, 1974). Such results suggested that first order CSs establish stimulusstimulus associations (i.e., identity predictions), whereas second order CSs instead directly elicit responses engendered during conditioning (via stimulus-response associations).…”